Figure F3. Comparison of vertical Guralp and geophone spectra for the same time interval (1300 hr) (high-and low-gain channels) in a window just before the gain change on JD360/2001. The geophone is an inexpensive sensor intended for use above its natural frequency of 4.5 Hz. It is encouraging that it resolves the microseism peak at ~0.25 Hz, but the geophone spectra rise quickly below 0.1 Hz because of instrument noise. Above ~2 Hz the geophone data are quieter than the Guralp. For each item listed, the first letter stands for geophone (E) or Gurlap (H), the second stands for high (H) or low (L) gain channels, and the third stands for vertical component (Z). Numbers in third position indicate horizontal components.

Figure F3. Comparison of vertical Guralp and geophone spectra for the same time interval (1300 hr) (high-and low-gain channels) in a window just before the gain change on JD360/2001. The geophone is an inexpensive sensor intended for use above its natural frequency of 4.5 Hz. It is encouraging that it resolves the microseism peak at ~0.25 Hz, but the geophone spectra rise quickly below 0.1 Hz because of instrument noise. Above ~2 Hz the geophone data are quieter than the Guralp. For each item listed, the first letter stands for geophone (E) or Guralp (H), the second stands for high (H) or low (L) gain channels, and the third stands for vertical component (Z). Numbers in third position indicate horizontal components.